Diplomatic: as usual.

Your client is responsible for approving the design. Don't blame the supplier!

Now: harrowing should be confined to flat faces. Side to side displacement imparts a degree of compaction in underlying layers and is not a good idea when the working face is concave. You're on a ticket to hell.

I have a personal hatred of harrows since one fell down during erection. Nobody was killed. Then when the chain tracks detached the buckets got buried because the sparkies had not interlocked the harrow and it carried on working. I hate them.

A scraper chain is the only answer and it is hard to imagine why harrowing was ever suggested. What sot of width was considered for the inboard harrow? Come on!

If that monstrous structure at the perimeter wall is a harrow then consider what could it possibly do? A scraper chain is a lot less complicated than a harrow and scraper chain..or what? ■

Hating harrows is too strong a word. Observed caution is far too mild.

The system on show reminds me of those fantasy machines dreamed up by Dravo and others during the 1980's.

This is an attempt to reduce building height by replacing the portal and outer boom with a full single scraper running over the bed. Power consumption goes through the roof and the material recovery is complicated by the standing wall which develops at the working face of the bucket line. This wall collapses regularly, it has to, and floods the chainway. Harrowing effectiveness is subject to the material top size. When the bigger stuff gets to the pile bottom it gets 'polished into a wall by the passing bucket edges. Those edges must have bite and if the material doesn't fall into the path no amount of harrowing is going to introduce material. Harrows cannot reach the full bucket width and generally rest on the face side and this inhibits their performance drastically.

There is no mechanical or structural advantage with this type of machine. A truss might have kept the weight down. A properly sized portal A frame would have done the job much better in terms of price and performance: in both directions. Your client has to start again or live with it. I feel DEM Bones again. Would this technology have identified the development of a standing wall? It might, with very detailed work.

Take heart, there are small harrows on some bucket wheel reclaimers which is a case of throwing 2 stones at 1 bird. Somewhere in the depths of the long forgotten eLibrary there was a description of a Californian bucket wheel which was tilted further round. It doesn't seem to have borne fruit and we can't dig the design up. We can only recognise that there are many crowding buckets in operation in various forms, again without harrows. ■